Adult Acoustic Immittance Measures

This group of tests measure the functional integrity of the eardrum and middle ear anatomy. These tests have become routine as they are sensitive to middle ear disorders even in persons with little or no hearing. Another advantage is that the test requires no behavioral response from the patient, making it an excellent test for young children. The first part of the test is the Tympanogram. Air pressure in the canal is varied above and below atmospheric level in the ear canal. The air pressure changes cause the eardrum, middle ear bones and associated muscles to react in specific ways. Depending on the resulting pattern, it indicates various disorders such as fluid (otitis media link), discontinuity of the ossicular chain link, perforated eardrum link and Eustachian tube dysfunction link.

Audiology Services ABR and Stacked ABR (Audiology Brainstem Response) Adult Acoustic Immittance ASSR Audiogram Electrocochleography ENG Instructions HINT Hearing Device Center Otoacoustic Emissions Pediatric Hearing Test Pediatric Acoustic Immittance Posturography

The second part is Acoustic ReflexThresholds. The stapedius muscle in the middle ear will contract in response to a loud sound; a reflex action designed to dampen loud sounds before they arrive at the cochlea or inner ear. Absence or presence of acoustic reflexes for various presentations may be important in the differential diagnosis of both peripheral and central disorders of the auditory system such as vestibular schwannoma link or facial nerve disorders link.

A third test is the Acoustic Reflex Adaptation (or Decay). Reflex decay is defined as a decline in the contraction of the muscle during a sustained stimulating signal. This is also helpful in interpreting and differentiating auditory test results. In patients with normal middle ear and reflex thresholds, there is no decay during the presentation of the tone. Patients with lesions of the cochlea, eighth nerve or auditory brainstem may have evidence of decay.

The Fistula Test is a special application of the tympanogram to test for certain causes of dizziness. Pressure is placed against the eardrum and decreased slowly. A positive response may be constituent with a perilymph fistula link which is an abnormal opening in the inner ear associated with dizziness and fluctuating hearing loss.

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